Effect Of Sodium Silicate Impregnation Modification On The Properties Of Chinese Fir Wood And The Joint Strength Of Right Angle Tenon

Cunninghamia lanceolata,as one of the important fast-growing forest tree species in southern China,has the advantages of fast growth,insect resistance,light-weight and wood aroma,and has become the object of attention of the industry and scholars.However,due to its loose structure,poor mechanical properties,poor dimensional stability,and flammability,its application in high value-added fields such as furniture,interior decoration and construction is restricted.Therefore,this article uses sodium silicate as the modifier and sodium fluorosilicate as the curing agent.Through"negative pressure-positive pressure" alternately acting on the wood,the uniform impregnation of the fast-growing Chinese fir wood is realized,and the water resistance and physical properties of the Chinese fir wood are improved.It has mechanical strength and endows Chinese fir wood with flame-retardant properties.Finally,the influence of silicate impregnation modification on the joint strength of right-angle tenon was studied.The results of this study are of great significance for promoting the development and application of enhanced modification technologies for Chinese fir wood.The main conclusions of the paper are as follows:(1)The influence of sodium silicate modulus,concentration and immersion time on the impregnation effect of Chinese fir wood was discussed,and a better process for impregnating Chinese fir wood with sodium silicate was obtained.Single factor tests show that as the modulus of sodium silicate increases,the physical and mechanical parameters of Chinese fir wood will increase accordingly.The modulus of sodium silicate is 3.4M,and the compressive strength of the modified material is 2.10 times that of the material;with the increase of sodium concentration,the mechanical strength of Chinese fir wood all presents a trend of first increasing and then decreasing.When the sodium silicate concentration is 20%,the mechanical strength of the modified wood is the highest;the difference of immersion time on the weight gain rate of Chinese fir wood is smaller.The overall trend shows an increase first,then a decrease,and finally tends to be flat.Orthogonal test analysis shows that under the conditions of sodium silicate modulus of 3.4M,concentration of 30%,and immersion time of 1h(negative pressure 20min,positive pressure 40min),the comprehensive performance of the sodium silicate modified material is the best.(2)The curing process parameters of sodium silicate were proved,and the curing mechanism of sodium silicate impregnated modified wood was revealed.The single factor test shows that when the curing agent concentration is 1.8%,the overall performance of Chinese fir wood is the best;at this time,compared with the group without curing agent,the loss rate of the modified wood is reduced by 25.97%,the weight gain rate,bending and compressive strength have been increased by 30%,37.1%and 10.6%respectively;through SEM and FT-IR analysis,it is found that the continuous filling of the modifier in the wood can improve the compressive strength of the wood better;after modification Chinese fir wood has formed a new Si-O-Si bond,indicating that sodium silicate acts on the wood in the form of physical filling and chemical bonds;XRD,TGA and CONE show that the crystallinity of fir increases,the thermal decomposition rate decreases,and the flame retardancy and smoke suppression properties enhanced.(3)By comparing the actual test results of the joint strength of the right-angle tenon before and after the modification of the fir,it is found that the flexural bearing capacity and the anti-pull bearing capacity of the modified right-angle tenon are better than that of the material.This result is roughly consistent with the finite element analysis result.